insulation and Moisture for a Seasonal Building
I have a small (700 sq feet) house/cottage in zip-code 48838, which is considered a Cold climate. I’m preparing to make some needed renovations, which will essentially strip it down to the studs (and some of them will be replaced … ), new windows, insulation, drywall, etc. It has historically been a 4-5 month cottage, as we usually winterized it in late September, although that date has been later over the last 40 years. The property was purchased by grandparents who used it as a way to escape city heat. It worked well, until about 10 years ago, when we finally bought window AC units…
Walls are currently 2×4, no sheeting, no insulation, 6″ ceder beveled siding, with homasote on the inside, except for a 50 year-old addition where it is the sheeting on the outside, and drywall on the inside.
I want to do typical stuff … plywood sheeting with a rain screen for siding, insulate the wall cavities, etc.
Adding foam insulation on the outside is problematic, since the roof overhang is quite small (about 4″), so I don’t wan’t to reduce that.
I’ve considered adding horizontal 2×3 on the inside, at sill level, top plate level, and 4′ for drywall. This gives an extra 1.5″ for blown in insulation.
But the real question comes down to moisture. For many years when we opened the place in the spring all was good. But the last decade or so has given us musty smells and stains from condensation. In addition a neighbor who had a mini-split installed needs to have it running all year set at a minimum of 50 degrees to keep his warranty intact, so I think there is something to the moisture issue.
So, after a long bit of background, here are my questions….
* How does sealing up a seasonal building impact moisture control?
* Considering my approach, and the difference from the usual scenario of a building occupied 24/7/365, where am I probably going to fail?
* Do I just need to suck-it-up, and now condition the building even when not occupied?
Thanks in advance for reading this long post, and any responses…
Replies
Maybe I asked this the the wrong way. If you do best practices regarding air sealing and insulation, how does this impact seasonal buildings?
If the building is properly sealed there is no need to condition it while it sits vacant.
In your case the air sealing becomes more important than the insulation as air leaking into the building is where the condensation will occur.
You should consider installing an energy recovery ventilator that will introduce tempered outside air into the building they come with an automatic timer than can operate for a set amount of hours each day which allows for some air exchange but should not introduce cold or humid air. There are many products but Panasonic makes a fairly good unit.
I have a vacation home at the Oregon coast, and the basement gets humidity year around. I've air sealed it, but I can't fully control it. I put a dehumidifier down there, and I the problem have been solved. I put it on a timer so it runs 4 hours a day - it's been going about 5 years with no issues.
Thank you for your replies. My plan now is to go forward as I said above, with sheeting and insulation, and monitor humidity. A dehumidifier would be useful, at least in the spring and fall when it won't freeze. I will also look in to an ERV. That seems like a really good solution as well.
In the past when we closed up for the fall we cut utilities (only utility was electricity, and by cut I mean throwing the main breaker). Going forward I won't be concerned about a bit of electricity in the off season, especially if it means making the place a bit nicer, healthier (no mustiness or rot), and comfortable. No worries about cost of running an ERV or dehumidifier. Only concern might be if there is a mechanical issue when I am 700+ miles away, although I think these things are quite reliable.